50 
than one colouring matter is formed after exposure of the 
leaves of plants to light. The colour clue to chlorophyll 
alone is probably seen in its purest state in the tender 
exquisite green of the young beech leaf or blade of corn. 
Other leaves, such as those of the oak, before attaining 
maturity have a decidedly yellow tinge, due it is supposed 
to the presence of an unusual proportion of phylloxanthin, 
the yellow colouring matter always accompanying chloro- 
phyll. Indeed, the lively contrast of tints seen in the 
foliage of the woods in early spring, the yellowish hue of 
the oak, and the pure green of the beech and larch relieving 
the sombre colour of the fir tree and the yew, affords one 
of the most pleasing sights of that delightful season. In 
early summer the young shoots of some trees, such as the 
oak, the sycamore, and the thorn, as well as the young 
leaves near the summit of each shoot, are tinged of a lively 
red, passing by degrees into the green of the mature leaves. 
The fruit wings of the sycamore are for many weeks in the 
summer similarly tinted, and the effect of the pink blush 
gradually shading off into the pale green of the wing tips is 
one that painters might introduce with advantage into 
their pictures of still life. This red colour is said to be due 
to erythrophy]l, the colouring matter formed in some leaves 
in the autumn, but whether the substance is in both cases 
really the same may be doubted. At the height of summer 
the foliage of trees displays a uniform green tint of varying 
depth, but it is probable that at this season the chlorophyll 
has already undergone a change, and I suspect that the 
sombre green of some leaves, such as those of the elm, in 
summer, is partly due to a product of decomposition called 
“modified chlorophyll,” which yields solutions of a much 
less lively colour than the chlorophyll from which it is 
formed. 
The summer stage is succeeded by that of the autumnal 
fading of foliage, a change so often observed that it needs 
